Combination lens mounting and film support for microfilm apparatus



Jan. 16, 1951 v. E. PRATT ET AL COMBINATION LENS MOUNTING AND FILMSUPPORT FOR MICROFILM APPARATUS 3 Sheets-Sheet 1 Filed March '7, 1947INVENTORS VERNEUR E. PRATT GEORGE F. GRAY ATTORNEYS Jan. 16, 1951 v. E.PRATT ET AL 2,538,269

COMBINATION LENS MOUNTING AND FILM SUPPORT FOR MICROFILM APPARATUS 3Sheets-Sheet 2 Filed March '7, 1947 4'5 x Y \O INVENTORS A l ERNEUR E.PRATT GEORGE F. GRAY ATTORNEYS Jan. 16, 1951 v E. PRATT ET AL 2,538,269

COMBINATION LENS MOUNTING AND FILM SUPPORT FOR MICROFILM APPARATUS FiledMarch 7, 1947 5 Sheets-Sheet 3 L Til 5,10

QElEIEEEEUDEX *NEEEEEEEDUE} NVENTORS l/ERNEUP E. PRATT GEORGE F. GRAYgwpwsea 15M A T TOPNE VS Patented Jan. 16, 1 951 COMBINATION LENSMOUNTING AND FILM SUPPORT FOR MICROFILM APPARATUS,

Verneur E.

Pratt and George F. Gray Norwalk, Conn.

Application March 7, 1947, Serial No. 732,971

This invention relates to lens mounting and film support for microfilmapparatus and more particularly to such mountings for use in microfilmdevices such as those disclosed in the copending applications:

Ser. No. 507,939, filed October 28, 1943 entitled Photographic Devicesand Method of Operating Same, now Patent No. 2,435,099 of Jan. 27,1948,.

and

, Ser. No." 547,131, filed July-29, 1944 entitled Bhotographic Devices,now Patent No. 2,478,980 of August 16, 1949.

I An object of this invention is to provide a lens mounting combinedwith a film support.

Another object is to provide a lens mounting with a slit forming memberforming part of the mount.

Another object is to provide a lens mounting wherein two lenses may beemployed in side-bysid'e relation to produce a double row. of images ona film. I

'A further object is to provide a combined lens mount and film supportthat will eliminate troubles now encountered due to temperature changesinthe apparatus.

:Other objects and advantages will be pointed out hereinafterparticularly in connection with the following brief discussion of theprior art' necessary to a proper understanding of the" invention.

While the following specification and accom-- panying drawings disclose,by way of illustration, preferred embodiments of the invention, it willbe understood that many changes can be made from 6 Claims. (01. 38-24Figure 6 is a front view of an alternate form of lens mount embodyingthe invention;

Figure '7 is a plan view of a film made by a camera employing the lensmount of Figure 8; Figure 8 is a side view of a twin-lens mountembodying the invention; and 7 Figures 9 and 10 are details of the mountshown in Figure 8.

, In Figure 1 is shown a lens mount and film support (often termed afilm gate) and illustrates diagrammatically a construction in commonuse. The framework of a camera is indicated at I0, and this supports ahorizontal member H upon which the lens J2 is mounted.

' The film support comprises a fixed platen I 3 secured to the frame [0having an opening (or a glass l4 therein) upon which the film F issupported and'to which it is pressed by a pressure plate [5 which ishingedly or otherwise movably supported onframe l0.

It will be understood that the pressure on the film is removed when thefilm is moved, the member l5 usuall being intermittently raised bysuitable mechanism (not shown) to permit of such film movement.

In such arrangements, it is necessary to very accurately construct orassemble all parts shown to obtain and maintain the dimensions X and Y.

, These and other difiiculties will be discussed in what is herein shownWithout departing from the invention as defined in the appended claims.

In the accompanying drawings:

Figures 1 and 2 are diagrammatic views of prior art lens mounts andtheir associated film supports or gates for the purpose of illustratingcertain features of prior art construction in order to 'clearlyunderstand the advantages and construction of the.instant invention, andhow it distinguishes from such prior art.

" Figure 3 is a front view of a lens mount embodying the invention.

in Figure- 3'.

Figure 4 is a side view of the lens mount shown ad 1, a d

connection with Figure 2.

The device Figure 1; can be used in fiow cameras where the photographingis done with the film in motion, provided the pressure plate 15Referring to Figure 2, a revolving drum [6 is mounted in bearing l1supported in the frame it.

means." jDetails-of devices employing this type of construction aref'shown in the co-pending appll-f cations previously mentioned.

The film is supported on this drum and is. 3 moved across theback focusof lens [2 by the rotation of the drum or by;;any other suitable Inpractically all types of microfilm cameras such as referred to above andin the aforesaid copending application, the copy support for the copy 2|is secured to or forms part of the frame work ID of the camera, so as tosupport the copy 2| in the front focus of the lens I2.

A suitable source of illumination is provided for illuminating the copyso that in the manner common to all cameras of this description, thelens of the camera receives the light reflected from the copy on thecopy support and an image on the film in the rear focus of the lens isproducedv in the usual manner.

While the construction shown in Figure 2 does not have some of thelimitations and objections of that shown in Figure 1, it inherently hasce1'- tain objectionable features in common therewith. Among these (andthe objects of the instant invention are their elimination) are:

(A) Much of the trouble in making production cameras to makehigh-resolution microfilm is in holding tolerances on the drums I6. Arun-out eccentricity of .0015 inch. on factory production does not givesatisfactory results, and in a certain commercial device, a limit of'run-out of .0003 inch is obtained by difficult and expensive selectionand manufacturing and assembling. This run-out affects the dimension Nof Figure 2 which corresponds to the dimension N of Figure 1 and is thecritical distance between the sensitive emulsion surface of film F andthe nodal point of the lens I2, a very critical dimension in short-focuslenses and a dimension that is adjusted to a fraction of a mm;

In making these" drums It, therefore, it is necessary to have themconcentric with axis a; to keep the diameter "11 the same on all' drumsand to have the shaft I8 supporting the drum perpendicular to the innerface of the support l0.

(B To maintain the dimension N on commercial machines so as to makevarious lens mounts interchangeable, it is obvious that the: axis a of.the drum shaft must be properly spaced from the outer surface Ila of thelens support. This means careful machining and location of the L memberH, the bearing- I! in frame 10, the bore in the: bearing for the shaft?l8, and the bore in the hub H! of drum 16.

Care is also necessary with the construction of Figure l asto themachining and relative location of the supports 13- and II and thepressure plate bearing support r (C): As yet, no way has beenfound-granted that the difficulties of manufacturing and assembling havebeen overcome--to compensate for the coefiicient of expansion of.aluminum. or other metal frame members Ht. Under operating con.- ditionswith a. 50 F. differential, the dimension b may vary as much as .0005inch, which seri-' ously and adversely affects. the resolution.

(D) With the construction shown in Figure 2, variations in the thicknessof the: emulsion on the film varies the dimension C, thereby causing avariation in. the important dimension N.

- From the foregoing, itcan be readily seen that to obtain the accuratedimensions necessary in high resolution microfilm apparatus, it isnecessary to work to. close. tolerances. Now, if in a given machine, alltolerances are plus, the device would. not produce good microfilm. Thisvhas necessitatedcareful. and. expensive inspection and selection ofpartsand, much; handfittingand has made, the interchanging, of lenses.between. ma.- chines in factory assembly very difli'cult and expensive.

(E) As it is difficult to maintain accurate dimensions in thesemachines, it has been customary to equip them with lenses such as shownat l2 which can be focussed, so that the user can focus the lens andthereby adjust the critical dimension N if for any reason ofmanufacturing or assembly it is not correct.

Now, these short-focus lenses require focussing (between film and lens)to the thousandth of an inchan adjustment that can only be made by anexpert having proper equipment and experience. Such a focussingoperation is usually entirel'y beyond the ability of the averageoperator of the machine. It is therefore highly desirable to employfixed focus lenses that can be easily changed in any given machine (orbetween machines) and whichare focussed at the factory and never requiresubsequent focussing as they are pre-focussed.

It is diflicult-in fact commercially impracticaL-to' do this with: thelenses mounted as shown in Figures 1 and 2 or in any other known manner,as the space behind the upper face of the lens mount and the film insome cameras is less than 5 mm, and the image of the copy 2| made by thelens on the film F cannot be observed, and even if seen is so small andin slit form that no one, even with a microscope, can properly see tofocus the lens; focussing, therefore, must be done on a trial-and-errorbasis by making sample film at various lens locations, processing saidhim, and by microscope examination selecting the best focus position andresetting the lens finally to that chosen best focus position. Such anoperation obviously cannot be performed by the user of the machine, sointerchangeable fixed focus lenses are not only highly desirable but area practical necessity.

Referring now to the instant invention, Figure 3 shows a lens mountembodying same. Here the framework In of the camera supports a turret orlens mounting frame 22 in which is mounted the lens system 23. Thelenses maybe adjustable in the mounting for convenience in assembly, butonce assembled, are never adjusted.

An arm 24 is vertically adjustable in the mounting 22 and is heldtherein by any suitable means such as the screw 25. This arm has ahorizontally extending platen 26' secured thereto which overlies the cap21 of the mounting, said" cap having the slit 28 therein.

The film F rests against the bottom arcuate surface of platen 26 withits emulsion sidetoward. the lens. By adjusting the arm 24', thecritical dimension N-the distance between the film and lens-is adjustedand once this is accomplished, the adjustment is fixed. Such ad justmentcan be made with the lens mount out of the camera.

The film is fed across the platen 26 in any suitable manner such, forexample,.as that shown in the co-pending applications hereinbeforementioned.

The rollers I 9 may be guide rollers or. feed rollers and may be mountedon the framework care of in the lens mount assembly which not onlysupports the lens. but also supports,- on the same assembly, the film infixed relation to the lens.

The platen 26 may be made of or faced with carbaloy or agate or someother hard non-wearing material, or may havetherein a roller 30, Figure5, against which the film F is held taut by the film-feeding mechanism,so that the roller revolves in a suitable bearin in the platen 2B. Thisroller may help to reduce friction on the film during its traverseacross the platen 26 while it receives images in the back focus of lens23.

The construction just described eliminates the difficulties discussed inconnection with paragraphs A and B hereof.

The construction shown in Figures 3 to 5 inclusive eliminates precisionWork on the film drive and supporting parts of the camera and confinesit to the lens mount per se. This being a relatively small device, it isnot seriously affected by temperature changes as discussed underparagraph hereof.

The construction shown in Figures 3 to inclusive does not eliminatetroubles due to variations in-the thickness of film stock orthe-emulsion thereon, as discussed under paragraph D hereof.

To eliminate difficulties due to variations in the film thickness C theconstruction shown in Figure 6 may be employed. Here, the platensupporting the film F takes the form of an arouate cap having the slit32 therein transverse the film. Here the critical distance N is betweenthe outer surface of the emulsion on film F and the nodal point of thelens 23 and, because of the relatively small dimensions of the one-pieceturret 33, this dimension can be made very accurately at low cost.

The platen block 3| can be made of any suitable material, same as theplaten 26, Figures 3 and 4, and the slit 32 may have rollers at eachside thereof, similar to roller 30, Figure 5.

The film F overlies the platen 3| and is held against same by anysuitable film-feeding mech- 'anism. If desired, a weight orspring-pressed member can be supported either on the turret 33 or on theframe ID to overlie the film F Figure 6 in order to press the filmdownagainst the slit in the arcuate cap 3|. Such a'member resembles member26 of Figure 3 and can be of any suitable construction as its onlypurpose is to gently press the film against the cap 3| so that samealways remains in contact therewith, covering the slit 32. Variations inthe thickness of' the film stock or emulsion cannot change the criticaldimension N, Figure 6.

As the lips of the slit 32 are in contact with the film, the openingagainst the film is clearly defined. A typical slit may be .030 inchwide x 1% inches long, and the curvature of the top of platen cap 3| maybe on a 2%; inch radius.

Because of the extreme accuracy that can be attained in a lens mountconstructed in accordance with the instant invention, a double lensmount for making twin rows of mm. images on one width of 35 mm. film canbe easily and cheaply constructed to be interchangeable with the 35 mm.single-row-one-lens mount previously described, and for use in the samecamera to produce duplicate micro-photographs side-by-side of the samecopy.

Such twin-images are shown in Figure 7 wherein 34 denotes the film andeach pair 'of duplicate images are shown at a, a b, b 0, 0

d, d; e, e Such a film is made in a fiow cam era by feeding copy a, forexample, through the camera and making two simultaneous exposures viathe twin-lens to produce images a, a etc. -To produce such twin imageswith a single tudinally along line 31 and remove 1 mm. from each edge toproduce the duplicate negatives.

Obviously, the 35 mm. negative film can be used to print positives,which are then split at 31 to produce duplicates.

The twin-lens mount will first be described as applied to existingcameras having drums l6 as described in connection with Figure 2. Suchcameras are described in the aforesaid applications.

Referring to Figure 8, the lens mount 38 supports the lenses 39, 4B. Thelenses must be exactly the same focal length in order that the rows 35,36 (Figure '7) of images can be brought into flow at the exact ratio ofmovement of film to copy. The lenses in Figure 8 may have a back focallength of 20 mm. in which case the space between the face of the cap 4|havingthe twin slits '42, 43 therein, is about'5 mm.

" As shown in Figure 9, the slits are each .050 inch wide andsufficiently long to form an image of the desired width to fit on the 16mm. film strip produced by slitting the 35 mm. strip as previouslydescribed.

' A baffle 44, Figure 10 extends transverse the cap between the slits toinsure that the twin images do not overlap. This may extend downwardinto the mount 38 about .170 inch, and may be about .095 inch thick,inch wide at the bottom and /4 inch wide at the top-tapered as shown inFigure 10. The cap 4| is close to the emulsion side of the film F (thedrawing Figure 9 is merely diagrammatic) and the division or baffle 4|therefore acts as a mask and not as -a vignetter or diaphragm.

, While the arrangement shown in Figure 8 does not eliminate all of thedifliculties listed under paragraphs A, B, C and D hereof, it is usefulin that old cameras can be used to make the film shown in Figure 7merely by substituting the twin-lens mount of Figure 8 for the existingsingle lenses therein.

Width of the fields of view 45, 46 of the lenses Figure 8 transverse thedirection of fiow are sufficient to include copy such as documents,etc., 14 inches wide when located in the focal plane of these lenses,and of course this depends upon the characteristics such as focallength, etc., of the lenses.

, To obtain the advantages set forth in connection with the lens mounts,Figures 3 to 6 inclusive, with a twin-lens mount as shown in Figure 8,it is only necessary to modify the twinlens mount as shown in saidFigures 3 to 6 inclusive.

For example, the mount Figure 8 may have the arm 24 and platen 26 ofFigures 3 and 4, with or without the roller 33 of Figure 5; or the mountFigure 8 can have the arcuate platen 3] on which the film F is supportedas described in connection with Figure 6.

All of the new lens mounts herein described-: may be removably mountedon the camera frame" ID. This may beaccomplished in any suitable;manner, such as by the provision of the gibs 45 7 Figure 3, the base 46of the mount being tapered as shown so that the mount can be pushed intothe gibs "and held between them and against vertical movement. A stop4'! can be secured to the frame l (Figure 8) to aid in positioning thelens mount in the camera.

As the single and double lens mounts can be made interchangeable, theycan be used at will in any given camera and are readily interchangeableamong cameras on a production line in the factory without the necessityof any re-focussing.

As the distance between the lens and. film are fixed. within the mountitself, mounts of the type shown .in Figures 3-6 inclusive and the twinlens mount as shown in Figure 8 modified in accordance with thedisclosure of Figure 6 can be mounted on an optical. bench or itsequivalent and thelens-to-film distance N very accurately adjusted in amanner that cannot be accomplished in photographic devices wherein thelens is mounted on one part of the framework and the film supported onanother, as described in connection with Figures 1 and 2. tion thereforeeliminates much of the precision work heretofore necessary and whichmade it not only di-ificu-lt to interchange lenses in any given camera,but made it practically impossible to change lenses bet-ween cameraswithout having to re-focusthe lens. The feeding elements for feeding thefilm from one reel to another may be of any desired type, such, forexample, as those shown in the aforesaid co-pendflng applications. Itwill be noted that the slit forming member such as the caps 3| "or M islocated between the feeding elements that drive the film and betweenwhich the film is tensioned. These caps therefore, press upon anddisplace the tensioned film in a plane perpendicular to the path oftravel of the film, the latter being held against the slit or slitswhich therefore define the exposed area or areas on the film, which ispreferably emulsion side down on the cap.

What is claimed is:

1. In combination with a mi rofilm camera wherein the copy and film arein fl w during photography, a combined lens mounting and film supportcomprising a tubular frame adapted to be mounted in said camera andpositioned a fixed distance from the copy support thereof, a lenscarried by said frame and adapted to re ceive light reflected from copyon said copy sllnport located in the focal field of said lens andproject an image of said copy, and means carri'ed by said frame forpositioning a film in the back focus of said lens to receive said image,including a slotted cap secured to the outer end of said frame andclosing the same, said cap being adjustable along a line parallel to theaxis of :said lens. 1

2. .In combination with a micro-film camera wherein the copy and filmare in flow during photography, a combined lens mounting and filmsupport comprising a tubular frame adapted to be mounted in said cameraand positioned a fixed distance from the copy support thereof, a lenscarried by said frame and adapted to receive light reflected from copyon said copy support located in the focal field of said lens and projectan image of said copy, and means carried by said frame for positioning afilm in the back tom-2s gaf'said lens to're'ceive said image, includaslotted cap secured to the outer end or said frame and closing the same,said cap com prising. a platen having a roller therein extend- The inven8 1 ing'trans-verse the optical axis of said lens and perpendicularthereto.

3. In combination with a microfilm camera wherein the copy and film arein flow during photography, a combined lens mounting and film supportcomprising a frame adapted to be mounted in said camera and positioned afixed distance from the copy support thereof, a lens carried by saidframe and adapted to receive light reflected from copy on said copysupport located in the focal field of said lens and to project an imageof said copy, and means including a convex cap carried by said frameforming a slit overlying said lens and adapted to define the area on afilm in said camera exposed to said lens to receive said image, saidframe and cap being-bodily removable from said camera as a unit,therelative position of said parts remaining fixed the while. V

4. In combination with a microfilm camera wherein the film and copy arein flow during photography, a combined lens mounting and mm supportcomprising a frame adapted to be supported on the framework of thecamera andpositioned a fixed distance from the copy support thereof, alens secured to said frame and adapted to receive light reflected fromcopy on said copy support located in the focal plane of said lens, meanscarried by said frame forming a slit over lying said lens and adapted todefine an area on afilm in said camera, said area receiving an image viasaid lens of copy on said copy support and means carried by said frameand spaced apart from said first means for positioning a film to overliesaid slit and support said film in the back focus of said lens, saidframe and slit formmeans being bodily removable from said camera as aunit, the relative position of said parts remaining fixed the while.

5. In photographic apparatus, a framework, means for continuously movinga film mounted on said framework, a lens mounting removably supported onsaid framework and having outwardiy extended portions adapted to engagesaid framework to position said mount thereon, said mount having a'cylindrical portion adapted to receive a lens mounting frame, acylindrical lens mounting frame and lenses therein adapted to beadjustably positioned in said cylindrical portion of said mount and tobe held therein in fixed relation thereto, and a slit-forming memberoverlying said lens mount and supported thereby and adapted to engageand support said moving film in the rear focus of said lenses, said lensmount, slit-forming member and lenses forming a unit structure removablefrom said photographic ,device and replaceable therein as a unit, therelative position of said parts remaining fixed the while.

'6. In a photographic device having a lens and a. mounting therefor,framework, a support socured to said framework and focal field of saidlens, a support for said lens mounting secured to said framework, a caphavbeing adapted to support .a film on its .arcuate; plane transverse.

upper face for transport in a the axis of said lens and spaced aparttherefrom. solely by said support, said lens being bodily removable fromsaid framework as positioned in the support and can? a unit the relativeposition of said parts remaining fixed the while. VERNEUR E. PRATT.

GEORGE F. GRAY,

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 288,025 Colt Nov. 6, 1883 910,322Schultze Jan. 19, 1909 1,616,636 Prosser Feb. 8, 1927 Number Number NameDate Wittel Jan. 6, 1931 Greibach Jan. 5, 1932 Bornmann Oct. 18, 1932Shull Sept, 11, 1934 Day Apr. 20, 1937 Hoyt Aug. 17, 1937 Schmidt Aug.7, 1945 Holbrook 1 Apr. 29, 1947 Tuttle June 8, 1948 FOREIGN PATENTSCountry Date France Jan. 21, 1941

